Multiplex electrical cable



(No Model.)

H. C. SPALDING.

MULTIPLEX ELECTRICAL CABLE.

No. 327,473. Patented Sept. 29, 1885.

N. PETERS. MvLitMr-phv. WMM. DA C.

UNITED STATES PATENT OFFICE.

HENRY O. SPALDING, OF BOSTON, MASSACHUSETTS.

MULTIPLEX ELECTRICAL CABLE.

SPECIFICATION forming part oi' Letters Patent No. 327,473, dated.September 29y 1885,

Application tiled December 14, 1F83. Renewed February 528, 1885.

To all whom it may concern:

Beit known that I, HENRY C. SPALDING, a citizen of the United States,residing at Boston, in the county of Suffolk and State of Massachusetts,have invented certain new and useful Improvements in Multiplex ElectricCables, of which the following is a specification, reference being hadto the drawing accompanying and forming a part of the same.

My invention relates to cables containing a group ofindividually-insulated electric conductorswhich constitute independentcircuits; and it consists in a novel construction of the cable, moreparticularly with reference to the arrangement of the conductors, bywhich induction or interference between and retardation in the severalcircuits is prevented.

Insulated electrical conductors have been twisted together in pairs andused as the leading and return conductors of a circuit, and severalpairs of these conductors have been assembled in a cable. Insulatedwires have also been braided or plaited together, with a view tolessening the effects of induction between them. It is well known,however, that neither of these plans accomplishes the desired objectbeyond a certain degree,which is not sufficient to remedy but onlyameliorate the trouble. In order, therefore, to overcome the inductionor interference that exists in multiple-circuit cables, I use twoinsulated wires twisted together for each circuit, and I braid or plaitthe several pairs together. I have found that this plan of arranging theconductors breaks up entirely the induced currents, so that theireffects are not perceptible, besides adding to the strength of thecable, and producing a round core of small diameter,upon which theinsulating-coatings are laid.

To still further improve the cable and to prevent the retardation andinductive electrical reactions, I inclose the braided conductors abovedescribed in one or more insulated metallic sheaths, and in thesefeatures my invention consists.

In the accompanying drawing the cable is shown with parts of each layerexposed.

A is the core composed of a group of strands, each consisting of twoconductors individually insulated and formed into a round braid. It isevident that a iiat braid rolled upon it- Self would also answer; butthe circular braid (No model.)

is preferable. The wires are preferably insulated by thin paper laid onan insulatingvarnish. They are then brought together in pairs andtwisted. The twisted strands are then formed into the braid, themachinery for making similar braids of other materials being suited tothis purpose.

Around the braid A is wound a strip of paper,b. Over thisisacoatofvarnish,c. Thenfollow, in the order named, aspirally-woundstrip of paper, d, a similarly-wound strip of metal foil, e, a coatingof resinous varnish, f, a strip of paper, g, a strip of metal foil, h, acoating of varnish, t', a paper strip, k, a coating of bituminouscompound, Z, a serving of strong twine, m, and a braided jacket orprotectingsheathing, O.

The specific manner of insulating and protecting the cable may begreatly varied. I prefer, however, the plan described, as it renders itvery easy to use one or more insulated metallic sheathings, the purposeof which, as I have more fully set forth in other applications nowpending, is to prevent electrical inductive reactions or retardation.

In a cable composed of strands of twisted wires braided together in themanner herein shown the positive and negative wires of each strand arein turn associated with the positive and negative wires of the otherstrands in a great variety of `juxtaposition at frequent intervals, andthus the induced currents are split up into infinitesimal fractions anddisappear.

Having now described my invention, what I claim is- 1. In an electricalcable,a group of conductors composed of a number of strands consistingof two insulated conductors forming a complete or round wire circuit,the strands being braided together in substantially the manner setforth.

2. In an electrical cable, the combination, with a core composed ofstrands braided together and each consisting of the two insulated wires,of a complete or round wire circuit of insulating or protective coatingsor layers surrounding said core, as set forth.

3. In an electrical cable, the combination, with a core 'composed ofstrands braided together and each composed of the two insulated wires,of a complete or round wire circuit ol' r) inductive and protectivecoatings and layers p surrounding` said coro, substantially ashereinloefore described.

In witness whereof I have hereunto signed my naine in the presence ofthe subscribing witnesses.

HENRY C. SPALDING.

Witnesses:

E. B. VELoH, ALEX. L. HAYES.

